Recently, for improved functionality, portable wireless devices provided with a communicating means built into a body thereof, for communication by means of RFID (Radio Frequency Identification), which is a contactless IC (Integrated Circuit) chip, and the like, are becoming common (for example, see Japanese Publication No. 2004-227046). In addition, as shown in Japanese Publication No. 2004-227046, although portable wireless devices are generally provided with a retractable main antenna outside a body thereof, for communicating with a mobile communication network, portable wireless devices with a main antenna built into a body thereof, for a more sophisticated design, are becoming common recently.
Incidentally, no conventional portable wireless device has been configured, even if a plurality of antennas are provided thereto, such that one antenna actively acts on any one of the other antennas. In other words, conventional portable wireless devices, even if a plurality of antennas are provided thereto, have been far from utilizing those antennas effectively.